[Qemu-devel] [PATCH v1] kvm: tolerate non-existing slot for log_start and log_stop

[David Hildenbrand <david@redhat.com>]

log_start might be called by memory.c just before registering the
section. So we can actually get a log_start without a region_add, which
we can silently ignore.

This makes current KVM code trigger an assertion
("kvm_section_update_flags: error finding slot").

Also, if we want to trap every access to a section, we might not have a
slot. So let's just tolerate if we don't have a slot.

Fixes: 343562e8fa22 ("kvm: kvm_log_start/stop are only called with known sections")
Reported-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 accel/kvm/kvm-all.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 90c88b517d..64de8461e0 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -394,8 +394,11 @@ static int kvm_section_update_flags(KVMMemoryListener *kml,
 
     mem = kvm_lookup_matching_slot(kml, start_addr, size);
     if (!mem) {
-        fprintf(stderr, "%s: error finding slot\n", __func__);
-        abort();
+        /*
+         * log_start() might be called before region_add(), and sometimes
+         * we don't have a slot as we want to trap every access.
+         */
+        return 0;
     }
 
     return kvm_slot_update_flags(kml, mem, section->mr);
-- 
2.13.5